Gender Boundaries Crumble in YA: The XY by Virginia Bergin

River drives her horse and cart through the woods as night falls. But when she sees a body lying in the middle of the road, her first emotion isn’t fear. It’s surprise.
The body doesn’t look like any she’s ever seen. It’s clearly human, but it has no breasts. There’s hair on its face, and a strange lumpiness rises between its legs.
It’s an XY. A male.
River has never encountered an XY before. Boys and men all live in hermetically sealed Sanctuaries where they won’t contract a lethal virus. The rest of the planet has been given over to women, who are immune. Any boy or man who leaves one of the Sanctuaries dies within 24 hours.
When River rouses the XY to consciousness, he attacks her, steals her knife, threatens to kill her, and eats her food without permission. River has never encountered anyone who would behave so badly before.
The XY – his name is Mason – says he’s been on the run in women’s country for five days. But only now does he fall ill. Losing his faculties, he releases her once again.
Watching him writhe on the road, River knows this male creature – this boy named Mason – is going to die. He knows it, too. He said as much to her.
She knows the humane thing to do. Her community’s code requires her to put him out of his misery. She’s given mercy to injured animals before.
But she just can’t bring herself to draw her blade across his neck. He’s a human being.
It takes three hours, but she carts Mason back to her village. The appearance of the first XY to survive the virus for more than a day reveals rifts in this community of women. Some race to heal him. Others want him to die. Caught in the middle, River finds herself lying for the first time in her life. Everything in her safe existence starts to unravel.